Device for controlling the feeding of hydraulic power devices

ABSTRACT

Device for controlling the feeding of a plurality of hydraulic power devices comprising a plurality of cavities, each communicating, at one of its ends, with one of the said power devices and in each of which slides a piston for feeding one power device, the said feed pistons being connected to a common driving member which displaces the same simultaneously in translation in one direction and the other, so that the said pistons discharge the hydraulic fluid from the cavities into the associated power devices and suck the said fluid from the power devices into the cavities according to their direction of displacement.

w a y 1 I" w r rte States tent [111 3,590,501

[72] Inventor Vittorio Louis Achille Bianchi 1,357,330 11/1920Laussucq.. 60/545 H 37 avenue Paul Dormer, Paris 116 (Seine), 2,736,2942/1956 Buehner 92/13 France 3,400,625 9/1968 Wrona 100/257 X [21] Appl.No. 818,230 3,407,710 10/1968 Weiss. 92/13 {22] Filed Apt. 22, 19691,831,238 11/1931 Ferris 60/545 X [45] Patented July 6,1971 1,744,8851/1930 Groene et a1. 60/545 X 3; Pnomy g 1968 Primary Examiner-Martin P.Schwadron 1 3:3 Assistant Examiner-A. M. Zupcic 1 Attorney-Steinberg &Blake [54] DEVIHCE FOR CONTROLLING THE FEEDING 011 D A I W gg fi fg i fgx AJBS'TRMIT: Device for controlling the feeding of a plurality ofhydraulic power devices comprising a plurality of cavities, [52] 10.8.CI 60/545, each c mmunicating at one of its ends, with one of the said92/133 92/146, 100/257, 100/269 power devices and in each of whichslides a piston for feeding [51] HIM. Cl. F1151) 7/00 ne power devicethe said feed pistmns bging connected to a 0 l h II, common drivingmember displaces the ame imultane. HA, H, HA; 92/145, 13 ously intranslation in one direction and the other, so that the said pistonsdischarge the hydraulic fluid from the cavities into [56} Rdemw cm theassociated power devices and suck the said fluid from the UNITED STATESPATENTS power devices into the cavities according to their direction of2,499,563 3/1950 Bill 60/545 E X displacement.

xxvg t PATENTED JUL6 I971 SHEET 3 BF 4 PATENTED JUL-6 ls'n SHEET 4 UF 4E%% L MW Q My M 0 Mb n K RN lDlEVlllClE FOR CONTROLLING 'lllllli llEEbllNG Oil llYlJRAUlLlC POWER DEVll CES The present invention hasessentially for its object a device for controlling the feeding ofhydraulic power devices, in particular power devices for actuating thepressing element of a press, shearing machine or the like.

It is known that presses, such as folding presses, cutting or punchingpresses, etc. comprise a member movable in translation, generallyconstituted by a plate or tray which comes to bear or act upon aworkpiece, for instance a metal sheet, or upon a cutting or punchingtool, the said workpiece or the said tool being held against a fixedmember constituted generally by a counterplate. In order to obtaincorrect folding or cutting, it is necessary that the movable plateremain, during its displacement, rigorously parallel with thecounterplate, in order that the folding or the cutting or punchingpressure be uniformly distributed whatever the location of the saidworkpiece or of the said tool on the plate may be, i.e. whatever thelocation at which the plate or the counterplate receives the load maybe.

The same goes for the shearing machines wherein the cutting blade mustbe displaced in a parallel direction to the counterplate.

A solution proposed to ensure a rigorously parallel displacement of theplate or the movable blade of a press or a shearing machine consists indriving the plate or the blade by means of pivoting connecting rodsactuated by a single double-acting power device.

However, this soltition is not applicable to all types of presses orshearing machines and it is necessary, in a number of such machines,that the plate or the like be actuated by a plurality of hydraulic powerdevices.

Now it has not been heretofore managed, in presses or the like, thepressing element of which is driven by a plurality of power devices, toobtain arigorously parallel displacement of the said pressing element,owing to the difficulties encountered in so controlling the variouspower devices that their actuation occur in perfect synchronism and soas to prevent dissymmetries from appearing in the long run between thepower devices, for instance differences between the travels of the powerdevices.

The present invention has essentially for its object a device forcontrolling the feeding of a plurality of power devices enabling toavoid the above-mentioned inconveniences and remarkable notably in thatit comprises a plurality of cavities, each communicating, at one of itsends, with one of the said power devices and in each of which slides apiston for feeding one power device, the said feed pistons beingconnected to a common driving member which displaces the samesimultaneously in translation in one direction and the other, so thatthe said pistons discharge the hydraulic fluid from the cavities intothe associated power devices and suck the said fluid from the powerdevices into the cavities according to their direction of displacement.

Owing to the use of a single driving member, there is obtained arigorously synchronous actuation of the various pistons being displacedin the various cavities and, consequently, rigorously synchronousfeeding and displacement of all the power devices associated with eachcavity.

According to another characteristic feature of the invention, means areprovided for feeding periodically the said cavities with makeuphydraulic fluid and maintaining constant the volume of hydraulic fluidcontained in each cavity and the power device associated therewith.

This supply of makeup fluid to the aforesaid cavities enables tocompensate for the leaks which inevitably occur in the entire hydraulicsystem, in particular in the power devices, and therefore to maintainconstant the mass of fluid being displaced between each cavity and thepower device associated thereto and, consequently to maintain constantthe travel of the power devices.

hollow ll whose outer diameter is very slightly less corr- The inventionensures rigorous parallelism of the plate or the like during itsdisplacement whatever the effort required from each power device may beand even in case of fluid leakage in one or several power devices.

According to still another characteristic feature of the invention, theaforesaid driving member is constituted by a hydraulically controlledelement movable in translation.

According to one form of embodiment of the invention, the aforesaidcavities are arranged side by side and open, at their ends opposite tothose communicating with the power devices, in a common chamber in whichis displaced the said driving member constituted by a hollow cylindermounted slidably with respect to a fixed piston and forming with thelatter a double-acting system.

According to a modified form of embodiment of the invention, theaforesaid cavities are aligned with one another and arranged coaxiallywith respect to a chamber in which is displaced the said driving memberconstituted by a piston provided with double-acting control.

Other characteristics and advantages of the invention will appear fromthe following description.

in the appended drawings given solely by way of example:

FIG. l is a sectional view of a device according to a first form ofembodiment of the invention, designed for the feeding of power devicesfor operating a press or the like, the feed pistons as well as thedriving cylinder of the said pistons being shown in the position theyoccupy at the end of their upward travel before the power devices arefed;

FIG. 2 is a sectional view upon the line ll-ll of FIG. l;

FIG. 3 is a view identical to H6. l, the feed pistons and the drivingcylinder being shown in the position they occupy at the end of theirdownward travel after the power devices are fed;

FIG. d is a sectional view of a device according to a second form ofembodiment of the invention, designed for feeding the power devices of apress or the like, the feed pistons and the driving piston being shownin the position they occupy before the power devices are fed;

FIG. 5 is a view identical to that of FIG. 4, the pistons being shown inthe position they occupy after the power devices are fed;

FIG. 6 illustrates diagrammatically and partially in section a devicefor controlling the power devices;

FIG. 7 is a top view of the device of FIG. 6.

According to the form of embodiment illustrated in FIGS. 1 to 3, thedevice designed to control four power devices of a press comprisesessentially a lower body or block 1 of generally cylindrical shape inwhich are provided four identical cavities 2 which are also cylindricaland whose axes are parallel with that of the body 1 and open on bothfaces of the latter, and an upper casing 3 in the shape of a cylindricalsleeve, the said casing 3 extending in prolongation of the lower body 1and being secured to the latter in a fluidtight manner. Two sideplates,namely a lower sideplate d and an upper sideplate 5 close the spacedefined by the assembly constituted by the body 1 and the casing 3. Thesideplates d and 5 are secured to the body 1 and to the casing 3respectively, in a fluidtight manner.

in each cavity 2 is mounted slidingly a piston 6 for feeding a powerdevice, the rod 7 of this piston 6 penetrating into the chamber 8defined by the casing 3.

Ports 9 provided in the lower sideplate 4 enable to make each cavity 2communicate with one hydraulic power device as will be explainedhereinunder.

Each feed piston 6 and its rod are traversed from end to end by acentral conduit Ml which opens, on the one hand, on the front face lidof the piston and, on the other hand, on the free end face 7:: of therod 7.

Each feed piston 6 divides the cavity 2 in which it is mounted into twoportions, namely a front portion 2a located below its front face 612 andrear portion 212 located above its rear fseeeat,

ln the dh lnber {8 defined by the casing 3 slides a cylindrical ii rthan the inner diameter of the said casing so as to ensure easyfitsliding; this cylindrical element also slides relative to a fixed piston12 concentric with the casing 3 and whose rod 13 is rigid with thesideplate 5. The cylindrical hollow element 11 comprises an innerchamber 14 allowing it to slide relative to the piston, this chamberbeing closed at its upper portion by a plate 15 provided with a centralopening for the passage of the rod 13. The fixed piston 12 divides thechamber M in which it is housed into two portions, namely a frontportion 14a and a rear portion Mb. Two conduits 16a and 16b both open atthe upper end of the rod 13 enabling the supply of hydraulic fluid intoeither the chamber Ma or the chamber 1417. It is seen that the assemblyconstituted by the cylindrical body 11 and the fixed piston 12 providedwith the rod 113 constitutes a doubleacting power device. Thecylindrical element 1i itself divides the chamber 8 in which it isslidingly mounted into a lower portion 8a comprised between the upperface to of the cylindrical block 1 and the front face 1 in of the saidcylindrical element and a rear chamber 8!; comprised between its rearface 1 1b and the sideplate 5. The portion 8a of the chamber 8communicates directly with the portion 2b of each cavity 2 and is on theother hand connected through the medium of a conduit 17 to a pan or thelike 18 containing makeup hydraulic fluid. The portion 8b of the chamber8 communicates with the exterior through two ports 19 and 26 provided inthe sideplates Each feed piston 65 is connected with the cylindricalelement 11 by resilient fixing means constituted by threaded rods or thelike 2l'screwed onto the front face 11a of the said cylindrical elementand passing through openings provided in the rods 7; springs 22 tend toapply the end face 7a of each rod 7 against the front face Illa of thecylindrical element ll.

Each cavity 2 comprised at its upper portion a shoulder 23 intended tolimit the upward travel of the feed piston 6. The location of theshoulders 23 is so selected that when the rear face 6b of the feedpiston 6 comes into contact therewith, the rear face 11b of thecylindrical element 1 1 is not yet in contact with the lower face 511 ofthe upper sideplate 5.

Each cavity 2 communicates through the medium of a pipe 25 connected tothe port 9 of the lower sideplate 4 with the chamber 26 of one of thefour power devices 27 (shown aligned for the sake of easy illustration)whose pistons 28 support the movable pressing plate 29 cooperating withthe fixed counterplate 30 (the plate and counterplate are illustrateddiagrammatically and partially for the sake of convenient illustration).A pressure-controlled contact 3i is provided on each conduit 25 topreclude overload of the said power devices.

The assembly constituted by the front portion 2a of each chamber 2 andthe chamber 26 of each power device 27 (as well as the connecting pipe)is filled with hydraulic fluid, this fluid being situated in the saidportion 2a or in the chamber 26 according to the position of the piston6 which thus ensures the feeding of the power device.

The supply of fluid to the double-acting power device constituted by thecylindrical. element l l and the fixed piston i2 is ensured by a pump 34sucking the fluid from a container 35 and supplying, through the mediumof a distributor 36 whose position is controlled automatically accordingto the displacement of the pressing plate, the pipes 37 and 38 connectedrespectively to the conduits 16a and Mb. The portion 812 of the chamber8 is connected directly to the hydraulic circuit supplied by the pump 34through a pipe 33 connected to the port 19 through the medium of aunidirectional calibrated valve 39.

A valve 40 connected through the medium of pipes 41 and 42 to thecontainer 35 and to the portion 8b of the chamber 8 controls thecommunication between the said chamber 8 and the said container. Thevalve 40 comprises a rod 43 rigid with a piston 44 moving in acylindrical enclosure 45. A spring 46 tends to maintain the valve 40spaced from its seat 47. The portion of the enclosure 45 located belowthe piston 44 is connected to the pipe 38, whereas the portion of thisenclosure 45 located above the piston 44 is connected to the pipe 33.

The operation of the device is as follows: the members of the devicebeing assumed to occupy the position shown in FIG. 1, when thedistributor'36 supplies the fluid delivered by the pump 34 into theconduit 16a through the medium of the pipe 37, the portion of thechamber 14 is supplied and the cylindrical element 11 is pusheddownwards, its front face 11a comes to bear against the rear faces 70 ofthe rods 7 of the feed pistons 6, so that the latter are also drivendownwards and discharge the hydraulic fluid contained in the frontportions 2a of the cavities 2 into the chambers 26 of the power devices27. The pistons 28 of the said power devices move up wards and drive thepressing plate 29 along with them. So long as the plate 29 does not comeinto contact directly or indirectly with the counterplate 30, the fluidexerts but little pressure on the calibrated valve 39, so that thelatter remains closed and prevents the fluid from penetrating into theportion 8b of the chamber 8. The negative or vacuum pressure created inthe portion 8b of the chamber 8 by the downward motion of thecylindrical element 11 results in a sucking of the fluid into the saidportion 8b from the container 35 through the pipe 41, the valve 430maintained open by the spring 46 and the pipe 42. When the pressingplate meets the sheet to be folded or the cutting or punching tool, theresistance offered to its feed motion leads to an abrupt increase in thepressure of the fluid and the latter opens the calibrated valve 39, sothat the fluid penetrates into the upper portion 8b of the chamber 8.The action of this fluid adds to that of the fluid penetrating in theportion Eda of the chamber 14 through the conduit 1.6a. Since the rearface lib of the cylindrical element ii is much greater than the sectionof the inner chamber M, there occurs an abrupt increase in the thrustexerted on the cylindrical element Ill and, therefore, on' the feedpistons 6 and, consequently, on the power devices 27, and the latter cantherefore provide the force required for the folding operation or forthe penetration of the cutting or punching tool into the material to becut or punched. The opening of the calibrated valve 39 also results inthat fluid pressure is applied to the portion of the enclosure 45located above the piston 44, so that the valve 40 is in closing contactwith its seat and the connection between the container 35 and theportion 8b of the chamber 8 is cut off. The cylindrical element ill.continues to move downwards until its front face 1 .21 a meets the upperface 1a of the block 1.

At that moment, the position of the distributor 36 is reversed, thefluid is admitted into the portion Mb of the chamber M through the pipe38 and the conduit 16b and the cylindrical element 11 moves intranslation upwards and drives along the feed pistons 6. The latter suckthe fluid contained in the chambers 26 of the power devices 27, so thatthe pistons 28 of the said power devices slide downwards and drive alongthe pressing plate 29 with them. When the feed pistons 6 come intocontact with the shoulders 23, their upward motion stops, whereas thatof the cylindrical element 111 continues until its rear face lib comesinto contact with the face 5a of the sideplate 5; as a result the frontface 11a of the element lli frees the apertures 16, thus enabling thelower portion 8a of the chamber 8 to communicate with the portions 2a ofthe cavities 2. Since the portion he of the chamber 8 is connected tothe pan l3, it results therefrom that if the hydraulic fluid does notfill completely the portion 8a of the chamber 8 as well as the portions2a and 2b of the cavities 2, fluid makeup takes place automatically byway of suction of the fluid contained in the said pan 13. It is alsoseen, in particular, that any leakage susceptible of occuring in thepower devices 27 is automatically compensated for. When fluid issupplied into the inner chamber 14b to drive the cylindrical element 11upward, hydraulic pressure is applied to the portion of the enclosure 45located below the piston 44, so that the valve so moves away from itsseat, thus reestablishing a communication between the portion db of thechamber 8 and the container 35 and, consequently, enabling the saidportion 81; of the chamber 8 to be emptied.

FIGS. 4 and 5 show another form of embodiment of a device also designedto control four power devices of a press. In these Figures, likereference numerals denote the same members as in FIGS. 1 to 3.

According to this form of embodiment, the device comprises essentially acylindrical casing 50 closed at both ends by sideplates 51 and 52 andprovided internally with four transverse equidistant partitions 53, sothat the interior of the easing 50 is divided into five compartments,i.e. four identical coaxially aligned cylindrical cavities and a chamber55 which is also cylindrical and also coaxial with the cavities 54. Ineach cavity 54 is slidingly mounted a piston 56 which divides it intotwo portions 540 and 54b. The portion 54a of each chamber 54 is providedwith a port 57 to which is connected the pipe 25 of each power device27. The assembly constituted by the portion 54a of each chamber 54 andthe chamber 26 of each power device 27 (as well as the connecting pipe)is filled, as in the previous case, with hydraulic fluid, this fluidbeing located in the portion 540 or the chamber 26 according to theposition of piston 56 which thus ensures the feeding of the powerdevices. The portion 54b of each chamber 54 communicates with theexterior through ports 58 and 59.

In the chamber 55 is mounted, also in a sliding manner, a piston 60which divides it into two portions 55a and 55b. Two ports 61a and 61bcommunicating with the portions 55a and 55b, respectively, of thechamber 55 enable to admit fluid on one or the other side of the piston60, thus allowing doubleacting control of the said piston. The ports 55aand 55b are connected to the pipes 37 and 38 respectively.

The feed pistons 56 and the driving piston 60 are rendered rigid withone another by rods 62 passing through the partitions 53, so that thefour pistons 56 are driven in translation in one direction and the otherby the piston 60.

Pipes 63 connected to the pipes 25 connect the chamber 26 of each powerdevice and the portion 54a of each cavity to the pan 18 containing themakeup hydraulic fluid through the medium of an obturating deviceconstituted by a valve 64 slidingly mounted in a casing 65 communicatingwith the pan 18 on the one hand and with the pipes 63 on the other hand.The valve 64 is subjected to the action of a spring 66 which normallyapplies it against the mouths67 of the pipes 63, thus cutting off thecommunication between the pan and the pipes (see FIG. 4) and to theaction of a rod 68 rigid with the piston 56 housed in the cavity 54located at the end of the casing 50 opposite to the chamber 55, this rodmoving the valve away from the mouths 67 and thus setting up acommunication between the pan and the pipes 63.

The operation of this device is as follows: the members being in theposition illustrated in FIG. 4, the admission of fluid through the pipe37 results in the feeding of the portion 55a of the chamber 55, so thatthe piston 60 moves from left to right and-drives the pistons 56 alongwith it. The hydraulic fluid contained in the portions 540 of thechambers 54 is delivered into the chambers 26 of the power devices 27whose pistons 28 move upwards until the pressing plate .29 comes intocontact, directly or indirectly, with the counterplate 30. As in thecase of the previous device, the fluid flowing in the pipe 37, duringthis first stage of the motion, exerts but little pressure on thecalibrated valve 39, the said pressure being insufficient to open thevalve. The negative pressure produced in the portions 54b of thecavities 54 by the displacement of the pistons 56 results in the suckingof the fluid from the container 35 through the pipe 41, the valve 40maintained open by the spring 46 and the pipe 42 connected to the ports59. When the plate meets the counterplate, the increase in fluidpressure in the pipe 37 opens the calibrated valve 39, so that the fluidpenetrates into the portions 54!; of the chambers 54 through the pipe 33and the ports 58. The action of the fluid on each-feed piston 56 adds tothe action of the fluid on the piston 60, thus resulting in considerableincrease of the thrust exerted on the pistons 28 of the power devices27. The opening of the calibrated valve 39 also results in moving thevalve 40 into closing contact with its seat and, consequently, in

cutting off the communication between the container 35 and the ports 59.When the assembly constituted by the feed pistons 56 and the drivingpiston 60 reaches the right-hand end of its travel (FIG. 5) the positionof the distributor 36 is reversed, the fluid admitted through the pipe38 penetrates into the portion 55b of the chamber 55 and pushes fromright to left the piston 60 which drives the pistons 56. The latter suckthe hydraulic fluid from the chambers 26 of the power devices 27 and thelatter retract. The fluid pressure in the inlet pipe 38 is applied tothe portion of the enclosure 45 located above the piston 44, so that thevalve 40 moves away from its seat and the fluid in the portions 54b ofthe chambers 54 is discharged into the container 35. When all thepistons 56 and 60 reach the end of their travel towards the left, therod 68 moves the valve 64 from its bearing position on the mouths 67, sothat if the hydraulic fluid does not fill the chambers 54a, fluid makeuptakes place by way of suction of the liquid from the pan 18.

Each power device 27 may advantageously be provided with a membercontrolling the travel of its piston, the said member being constitutedby a threaded rod 70 traversing the bottom wall of the chamber 26 and,therefore, penetrating into the latter (FIG. 6). The threaded rod 70 ismounted in a rotatable sleeve 71 which is also threaded. The rotation ofthe sleeve 71 results in an upward or downward motion of the threadedrod which constitutes an adjustable stop enabling to adjust at will thelower position of the piston 28 and, therefore, the travel of thispiston.

Simultaneous rotation of the threaded rods 70 of the various powerdevices 27 can be performed by an electric motor 72 which drives,through the medium of a reducer 73, one of the sleeves 71, the othersleeves being connected to the sleeves driven by means ofa chain 74meshing with gears 75 rigid with each sleeve. This rotation may also beensured by a hydraulic motor.

It should be noted that this adjusting device, owing to the fact that itenables to move the pistons 28 upwards, may be used to operate the powerdevices 27 which, in this case, are controlled mechanically.

Of course, it is also possible to use instead of the single-acting powerdevices 27 wherein the return motion of the piston takes place bygravitation, power devices whose piston is subjected to the action ofareturn spring or, alternatively, doubleacting power devices, especiallyin the case where the motion of the pressing plate takes placedownwardly instead of upwardly as shown.

Of course, the invention is by no means limited to the forms ofembodiment described and illustrated, as the latter have been given onlyby way of example. In particular, it comprises all the meansconstituting technical equivalents to the means described as well astheir combinations, should the latter be carried out according to thespirit of the invention. It is apparent from the above description thatin both of the embodiments, namely that of FIGS. 13 and that of FIGS. 4and 5,

' there is a driving piston means movable from a given starting positiontoward an end position and then back to the starting position. Thisdriving piston means is formed in the embodiment of FIGS. l-3 by thecylindrical body 11 and in the embodiment of FIGS. 4 and 5 by theseveral pistons 56 and 60. In the embodiment of FIGS. 1-3, the stopstructure 23 by preventing the feed pistons 6 from following thecylindrical body 11 when the driving piston means formed by the latterreturns to the starting position of FIG. 1 forms through the resultingcoaction between the feed pistons 6 and the driving piston means 11 tocreate the gap therebetween a means for automatically placing thehydraulic assembly in communication with a source of makeup fluid uponreturn of the driving piston means to its starting position. Thishydraulic assembly is of course formed by the cylinder surrounding thedriving piston means and the latter. In the embodiment of FIGS. 4 and 5,the rod 68 by actuating the valve 64 upon return of the driving pistonmeans 56, 60 to its starting position shown in FIG. 4 again forms forthis embodiment a means placing the hydraulie system formed by thedriving piston means 56, 60 and the outer casing 50 automatically incommunication with the source of makeup fluid 18 when the driving pistonmeans of this embodiment returns to its starting position.

Furthermore, it is to be noted that in both of the above embodiments thedriving piston means has a first working area to be acted upon byrelatively low-pressure fluid and a second working area whichcommunicates with a low-pressure source while the first area is workedon by the low-pressure fluid. Thus, in the embodiment of FIGS. l3 thecross-sectional area of the front portion 14a of the inner chamber 14forms the first area of this driving piston means 11 which initially isacted upon by the low-pressure fluid while the area formed by the rearface llb forms the second area of the driving piston means whichcommunicates through the valve 40 with the source of low-pressure 35while the first area of the piston means is acted upon by thelow-pressure fluid. The same is true of the embodiment of H08. 4 and 5where it will be seen that only the area of piston 60 directed towardthe chamber portion 55a forms the first area which initially is actedupon by the low-pressure fluid while at the same time the severalchambers 54b, and thus the areas of the several pistons 56 directedtoward these chambers communicate through the several ports 59 and thevalve 40 with the source of low-pressure 35.

In both of the embodiments the calibrated valve 39 forms a means whichresponds to engagement with the load for automatically introducing fluidat a relatively high pressure to act on the first working area of thepiston means as well as to automatically actuate the valve means 40 forcutting off communication between the second area of the driving pistonmeans and the source of low pressure while placing this second area ofthe driving piston means also in communication with the relativelyhigh-pressure fluid.

As a result, there is an increased driving force not only because of theincrease in the pressure of the fluid acting on the first working areaof the driving piston means but also because the second area of thedriving piston means becomes effective with the higher fluid pressure toincrease the driving force.

Finally, it is to be noted in connection with FIGS. 6 and 7 that theseveral threaded stop screws 70 are mechanically driven simultaneouslyto determine an end position for each of the pistons 28 ofeach powermeans 27. This power means is of course normally driven by the fluidpressure assembly constituted by the above-described driving pistonmeans and the casing surrounding the latter as well as the connectionsbetween this fluid pressure assembly and the several power means 27.However, one of the great advantages of this construction isthat themechanical drive means for determining the positions of the stop means70 is also capable of acting through the stop means 70 for advancing thepistons 28 of the several power means 27, so that in the event offailure of the fluid pressure assembly it is still possible to operatewith the several power means 27.

What I claim is:

1. In a hydraulic press having a movable pressing element, a pluralityof hydraulic power devices for actuating said pressing element, each oneof said hydraulic power devices having a chamber, a reciprocally movingpiston in said chamber and a stop member of adjustable length, a devicefor controlling the feeding of said hydraulic power devices, said devicecomprising a plurality of cavities containing a hydraulic fluid, eachcavity communicating, at one of its ends, with one of the said powerdevices, a movable feed piston in each one of said cavities for feedingthe associated power device, an inner chamber, a hydraulicallycontrolled and reciprocally movable driving member located in saidchamber and connected to said feed pistons whereby the latter aredisplaced simultane ously in translation in one direction or the other,and discharge said hydraulic fluid from said cavities into saidassociated power devices or suck said fluid from said power devices intosaid cavities according to their direction of dis placement, makeuphydraulic fluid container connected to said cavities and means forfeeding periodically said cavities with said makeup hydraulic fluid andmaintaining constant the volume of the hydraulic fluid contained in eachcavity and its associated power device, said cavities being arrangedside by side and open, at their ends opposite to those-communicatingwith said power devices, in said inner chamber and said driving memberbeing constituted by a hollow cylinder having a front wall and rearface, said cylinder being mounted slidably relative to a fixed pistonand within which a pressure fluid is admitted for causing it to movewith respect to said fixed piston, each aforesaid feed piston beingprovided with a rod having a free end connected by means of resilientfixing members to the front wall of the said cylinder, so that it isalternately pushed by said cylinder or drawn by the latter through themedium of said resilient fixing members.

2. A hydraulic press according to claim 1, wherein each aforesaid feedpiston and its associated rod are traversed by a conduit opening at thefree end of said rod the travel of said feed piston being slightly lessthan that of the said cylinder, so that at the end of each stage oftraction of the said feed piston, the front face of said cylinder movesaway from said rodand frees said conduit, thus making each cavitycommunicate with said inner chamber, the latter communicating with saidmakeup hydraulic fluid container.

3. A hydraulic press according to claim 2, wherein said inner chamber isconnected at its end opposite to that communicating with the aforesaidcavities, to a hydraulic circuit operating the aforesaid cylinder, acalibrated valve being in said hydraulic circuit to control the inflowof fluid into the said chamber, the action of said fluid on the rearface of the said cylinder adding to the action of the fluid admittedinto said 4 cylinder.

4. A hydraulic press according to claim 1, wherein the aforesaid stopmember of each one of said power devices is constituted by a threadedrod mounted in a rotatable threaded sleeve.

5. A hydraulic press according to claim 4, wherein the aforesaid sleevesare rotated jointly by a transmission chain driven by a motor.

6. In a hydraulic press having a movable pressing element, a pluralityof hydraulic power devices for actuating said pressing element, each oneof said hydraulic power devices having a chamber, a reciprocally movingpiston in said chamber and a stop member of adjustable length, a devicefor controlling the feeding of said hydraulic power devices, said devicecomprising a plurality of cavities containing a hydraulic fluid, eachcavity communicating, at one of its ends, with one of the said powerdevices, a movable feed piston in each one of said cavities for feedingthe associated power device, an inner chamber, a hydraulicallycontrolled and reciprocally movable driving member located in saidchamber and connected to said feed pistons whereby the latter aredisplaced simultaneously in translation in one direction or the other,and discharge said hydraulic fluid from said cavities into saidassociated power devices or suck said fluid from said power devices intosaid cavities according to their direction of displacement, makeuphydraulic fluid container connected to said cavities and means forfeeding periodically said cavities with said makeup hydraulic fluid andmaintaining constant the volume of the hydraulic fluid contained in eachcavity and its associated power device, said cavities being aligned withone and another and arranged coaxially with said inner chamber, saiddriving member being constituted by a driving piston rigid with saidfeed pistons, so that the said feed pistons are driven simultaneously inone direction or the other by driving piston, each power device and itsassociated cavity being connected to said makeup hydraulic fluidcontainer through the medium of a valve controlled by the displacementof all the aforesaid pistons, the said valve being provided to set upthe communication at the end of each sucking stage of the aforesaid feedpistons.

sleeve, the aforesaid sleeves being rotated jointly by a transmissionchain Jriven by a motor.

1. In a hydraulic press having a movable pressing element, a pluralityof hydraulic power devices for actuating said pressing element, each oneof said hydraulic power devices having a chamber, a reciprocally movingpiston in said chamber and a stop member of adjustable length, a devicefor controlling the feeding of said hydraulic power devices, said devicecomprising a plurality of cavities containing a hydraulic fluid, eachcavity communicating, at one of its ends, with one of the said powerdevices, a movable feed piston in each one of said cavities for feedingthe associated power device, an inner chamber, a hydraulicallycontrolled and reciprocally movable driving member located in saidchamber and connected to said feed pistons whereby the latter aredisplaced simultaneously in translation in one direction or the other,and discharge said hydraulic fluid from said cavities into saidassociated power devices or suck said fluid from said power devices intosaid cavities according to their direction of displacement, makeuphydraulic fluid container connected to said cavities and means forfeeding periodically said cavities with said makeup hydraulic fluid andmaintaining constant the volume of the hydraulic fluid contained in eachcavity and its associated power device, said cavities being arrangedside by side and open, at their ends opposite to those communicatingwith said power devices, in said inner chamber and said driving memberbeing constituted by a hollow cylinder having a front wall and rearface, said cylinder being mounted slidably relative to a fixed pistonand within which a pressure fluid is admitted for causing it to movewith respect to said fixed piston, each aforesaid feed piston beingprovided with a rod having a free end connected by means of resilIentfixing members to the front wall of the said cylinder, so that it isalternately pushed by said cylinder or drawn by the latter through themedium of said resilient fixing members.
 2. A hydraulic press accordingto claim 1, wherein each aforesaid feed piston and its associated rodare traversed by a conduit opening at the free end of said rod thetravel of said feed piston being slightly less than that of the saidcylinder, so that at the end of each stage of traction of the said feedpiston, the front face of said cylinder moves away from said rod andfrees said conduit, thus making each cavity communicate with said innerchamber, the latter communicating with said makeup hydraulic fluidcontainer.
 3. A hydraulic press according to claim 2, wherein said innerchamber is connected at its end opposite to that communicating with theaforesaid cavities, to a hydraulic circuit operating the aforesaidcylinder, a calibrated valve being in said hydraulic circuit to controlthe inflow of fluid into the said chamber, the action of said fluid onthe rear face of the said cylinder adding to the action of the fluidadmitted into said cylinder.
 4. A hydraulic press according to claim 1,wherein the aforesaid stop member of each one of said power devices isconstituted by a threaded rod mounted in a rotatable threaded sleeve. 5.A hydraulic press according to claim 4, wherein the aforesaid sleevesare rotated jointly by a transmission chain driven by a motor.
 6. In ahydraulic press having a movable pressing element, a plurality ofhydraulic power devices for actuating said pressing element, each one ofsaid hydraulic power devices having a chamber, a reciprocally movingpiston in said chamber and a stop member of adjustable length, a devicefor controlling the feeding of said hydraulic power devices, said devicecomprising a plurality of cavities containing a hydraulic fluid, eachcavity communicating, at one of its ends, with one of the said powerdevices, a movable feed piston in each one of said cavities for feedingthe associated power device, an inner chamber, a hydraulicallycontrolled and reciprocally movable driving member located in saidchamber and connected to said feed pistons whereby the latter aredisplaced simultaneously in translation in one direction or the other,and discharge said hydraulic fluid from said cavities into saidassociated power devices or suck said fluid from said power devices intosaid cavities according to their direction of displacement, makeuphydraulic fluid container connected to said cavities and means forfeeding periodically said cavities with said makeup hydraulic fluid andmaintaining constant the volume of the hydraulic fluid contained in eachcavity and its associated power device, said cavities being aligned withone and another and arranged coaxially with said inner chamber, saiddriving member being constituted by a driving piston rigid with saidfeed pistons, so that the said feed pistons are driven simultaneously inone direction or the other by driving piston, each power device and itsassociated cavity being connected to said makeup hydraulic fluidcontainer through the medium of a valve controlled by the displacementof all the aforesaid pistons, the said valve being provided to set upthe communication at the end of each sucking stage of the aforesaid feedpistons.
 7. A hydraulic press according to claim 6, wherein theaforesaid stop member of each one of said power devices is constitutedby a threaded rod mounted in a rotatable threaded sleeve, the aforesaidsleeves being rotated jointly by a transmission chain driven by a motor.